Red-Grape Compound May Improve Diabetes

THURSDAY, Oct. 22 -- New research provides further insight into how a health-boosting compound found in red grapes may help the body fend off type 2 diabetes.

But scientists have only seen the effect in mice who received injections in the brain, and no evidence has emerged that consuming red wine or other products made with grapes will alleviate the blood sugar disease.

The findings do tell scientists about how the compound known as resveratrol works on the brain, said senior study author Roberto Coppari.

If scientists know that the brain is a "major player," then drug companies working on related research "will focus on a drug that will penetrate the brain," said Coppari, an assistant professor of internal medicine at University of Texas Southwestern Medical Center in Dallas.

Scientists have been excited about resveratrol, which is found in red grapes, red wine, pomegranates and some other foods, appears to extend the life spans of mice, even those fed a high-fat diet. Resveratrol appears to mimic the effects of severely restricting food intake, which helps a wide variety of animals live longer, Coppari said.

"You can take the spider, fish, and almost every animal in the planet, and give 70 percent of what the animal would normally eat, and you'll see beneficial effects," he said. "Of course, calorie restriction is very difficult to impose on people. You will feel hungry all the time."

In the new study, Coppari and colleagues looked at the effects of resveratrol on diabetes, not life span. Previous research has suggested that the compound helps the body fight off diabetes.

The researchers injected either resveratrol or a placebo into the brains of diet-induced and diabetic mice and watched to see what happened.

Over five weeks, insulin levels returned to half of normal levels in the mice that got the resveratrol injections, even though they were on high-fat diets. Researchers suspect resveratrol activated proteins in the brain called sirtuins.

The insulin levels in the other mice went up, apparently because of their diets.

So why not drink red wine to get the same effects? It won't work, Coppari said, since the amount of resveratrol in red wine is too low. Then there's the matter of the barrier between the bloodstream and the brain, which keeps things out of the brain.

"Clearly, administration of drugs to patients directly into the brain for chronic diseases is not feasible or realistic," said Lindsay Brown, of the University of Queensland's department of physiology and pharmacology in Australia.

"But this study may lead to the development of compounds that are more effective in crossing from the blood to the brain than is resveratrol," said Brown.

The study, which was supported by the American Heart Association, National Institutes of Health and American Diabetes Association, was published online in advance of its print publication in the December issue of the journal Endocrinology.